This makes a big, rich pie, be sure and use a 10" pan or it overflows in the oven.
Crust: Combine 1 and 3/4 cup flour, 1/4 cup sugar, 1 tsp. cinnamon, 1/2 tsp. salt. Cut in 1/2 cup plus 2 T. butter (one and 1/4 sticks), 1/4 cup water or apple cider. (can be made in stand mixer. It's worth using the apple cider, makes the crust delicious). Roll out the crust, ease into a 10" pie pan and flute.
Filling: 8 McIntosh apples (if they're big you'll only need 6-7), peeled & sliced.
Combine 1 and 2/3 cup sour cream, 1 cup sugar, 1/3 cup flour, 1 egg, 2 tsp. vanilla, 1/2 tsp. salt, and mix well. Stir in the apples and spread in the crust.
Bake: Bake at 450 degrees for 10 minutes. Reduce heat to 350 and bake 'til slightly puffed and golden brown, 40 minutes.
Topping: Combine 1 cup chopped walnuts, 1/2 cup flour, 1/2 cup sugar, 1 T. cinnamon, pinch of salt, 1/2 c. butter. Mix until crumbly. Spoon over pie and bake 15 minutes longer.